A vacuum motor is known as an actuator used for a driving source such as a vacuum pump, a turbo molecular pump or the like. The vacuum motor is equipped with a rotor and a stator comprising an electromagnet for rotationally driving the rotor. As well known, the electromagnet is formed by winding a magnetic coil around a core. A laminate steel plate is used as the core constituting the electromagnet. The laminate steel plate is constructed by adhesively attaching plural thin steel plates to one another with resin adhesive agent.
It is required for the vacuum motor to keep the inside of the case to a high-vacuum atmosphere. In the conventional vacuum motor, a rotor and a stator are disposed in the case (JP-A-10-288191), and also a laminate steep plate is used as the core of an electromagnet constituting the stator, so that it is difficult to keep a high vacuum atmosphere in the case due to an effect of gas discharged from resin adhesive agent sandwiched between laminate steels.
Furthermore, when the vacuum motor is required to be operated under high temperature, a large amount of gas is discharged from resin adhesive agent sandwiched between laminate steel plates, it is further difficult to form a high-vacuum atmosphere.
The present invention has been implemented in view of the foregoing situation, and has an object to provide an actuator that can form a high-vacuum atmosphere in a case and also hold sufficient durability under operation at high temperature.